Cancer remains responsible for a large part of deaths worldwide. At present most treatments for cancer still give rise to unwanted side-effects. In this thesis, a treatment that combines both chemo- and radiotherapy to reduce the side-effects of chemotherapy is reported. Instead of allowing the drug to spread through the whole body and also targeting fast dividing healthy cells, a chemotherapeutic drug is encapsulated in a polymeric nanocarrier. In addition, the nanocarrier encapsulates another molecule, a photosensitizer. The photosensitizer can be activated by visible light to produce singlet oxygen and in previous experiments was shown to be able to induce release when exposed to ionizing radiation. In a yet unknown process this will act as a switch, leading to the polymeric nanocarrier releasing the chemodrug. This allows inducing a more precise release at the tumor by focusing the radiation locally. To enhance the local radiation effect, gold nanoparticles are introduced in the nanocarrier in addition to the other particles present. In this research the first steps in validating this type of treatment were taken by investigating the release of the chemotherapeutic drug upon irradiation of the nanocarriers, as well as testing the viability of human glioblastoma cancer cells containing the nanocarriers before and after irradiation. New methods to measure. the release from the nanocarriers were tested, different radiation types were investigated, and two different cell viability assays were used. The results indicate no clear effect of the gold nanoparticles on the release of the nanocarriers, but the interesting interaction between the different particles in the nanocarriers invites for further studies